Robotic surgical systems such as those used in performing minimally invasive surgical procedures offer many benefits over traditional open surgery techniques, including less pain, shorter hospital stays, quicker return to normal activities, minimal scarring, reduced recovery time, and less injury to tissue. Consequently, demand for minimally invasive surgery using robotic surgical systems is strong and growing.
One example of a robotic surgical system is the da Vinci® Surgical System from Intuitive Surgical, Inc., of Sunnyvale, Calif. The da Vinci® system includes a surgeon's console, a patient-side cart, a high performance 3-D vision system, and Intuitive Surgical's proprietary EndoWrist™ articulating instruments, which are modeled after the human wrist so that when added to the motions of the robotic arm assembly holding the surgical instrument, they allow a full six degrees of freedom of motion, which is comparable to the natural motions of open surgery.
The da Vinci® surgeon's console has a high-resolution stereoscopic video display with two progressive scan cathode ray tubes (“CRTs”). The system offers higher fidelity than polarization, shutter eyeglass, or other techniques. Each eye views a separate CRT presenting the left or right eye perspective, through an objective lens and a series of mirrors. The surgeon sits comfortably and looks into this display throughout surgery, making it an ideal place for the surgeon to display and manipulate 3-D intraoperative imagery.
While performing a surgical procedure, vibrations experienced on a tip of a surgical instrument may cause control problems for a surgeon. For example, such vibrations may make it difficult for the surgeon to perform fine surgical manipulations of tissue, needles and sutures. A flexible robotic arm assembly, especially when mounted on flexible setup arms and/or with unbalanced link masses and inertias, may cause such vibrations to easily get started by fast transient motions commanded by the surgeon on a master manipulator. The vibrations in this case may be at the resonant frequency of the robotic arm assembly, or that of a mechanical structure supporting the robotic arm assembly. In addition, vibrations may also occur as a result of any non-smooth command motion of the master manipulator.
Although a low pass filter may be employed in a teleoperation control system to filter out master manipulator motion commands that may cause vibration occurring at frequencies above those of intended surgical motion, such a low pass filter also inserts delay into the teleoperation system, specifically between the master commanded motion and the actual robotic arm assembly motion. Unfortunately, when force feedback indicative of forces being asserted against the tip of the surgical instrument is provided back to the surgeon through the master manipulator, the delay added to the teleoperation control system by the low pass filter tends to drive the control system unstable. This greatly limits either the ability to filter out undesirable vibrations or the ability of the system to provide the surgeon with haptic force feedback.